A dramatic change is currently on the horizon in the sector of visual display unit and illumination technology. It will be possible to manufacture flat displays or illuminated surfaces with a thickness of less than 0.5 mm. This new technology is based on the principle of OLEDs, Organic Light Emitting Diodes.
Such components consist predominantly of organic layers. At a voltage of, for example, 5 V to 10 V, electrons pass from a conductive metal layer, for example from an aluminum cathode, into a thin electron conduction layer and migrate in the direction of the anode. This consists, for example, of a transparent but electrically conductive thin indium tin oxide layer, from which positive charge carriers, so-called holes, migrate into an organic hole conduction layer. These holes move in the opposite direction compared to the electrons, namely towards the cathode. In a middle layer, the emitter layer, which likewise consists of an organic material, there are additionally special emitter molecules where, or close to which, the two charge carriers recombine and lead to uncharged but energetically excited states of the emitter molecules. The excited states then release their energy as bright emission of light, for example in a blue, green or red color. White light emission is also achievable. In some cases, it is also possible to dispense with the emitter layer when the emitter molecules are present in the hole or electron conduction layer.
Crucial for the construction of effective OLEDs are the light emitting materials (emitter molecules) used. These can be realized in different ways, namely by using purely organic or organometallic molecules as well as complex compounds. It can be shown that the light output of the OLEDs with organometallic substances, so-called triplet emitters, can be significantly greater than of purely organic materials. Due to this property, the further development of the organometallic materials is of high significance. Using organometallic complexes with high emission quantum yield (transitions including the lowermost triplet states to the singlet ground states), it is possible to achieve a particularly high efficiency of the device. These materials are often called triplet emitters or phosphorescent emitters.
Against this background, it was the object of the present invention to provide novel compounds, which are suitable for optoelectronic components.